Ovule

Reproductive System. The primary PGs are intimately involved in reproductive physiology (67). PGE2 and PGP2Q, are potent contractors of the pregnant utems and intravenous infusion of either of these compounds to pregnant humans produces a dose-dependent increase in frequency and force of uterine contraction. PGI2 and TXA2 have mild relaxant and stimulatory effects, respectively, on uterine tissue. The primary PGs also play a role in parturition, ovulation, luteolysis, and lactation and have been impHcated in male infertility. 

Nystatin (100,000 lU) is also available in combination with neomycin sulfate [1405-10-3] (35,000 lU), polymyxin B sulfate [1405-20-5] (35,000 lU), acetarsol [97-44-9] (150 mg), and dimethicone [8050-81-5] (2,500 mg). One or two ovules per day are inserted vaginaHy for at least 6—12 days. This combination has an antibacterial, antimycotic, and antitrichomonas action (see also Antibiotics, oligosaccharides Antiparasitic agents, antiprotozoals). 

The concept of hormonal control of ovulation first appeared in 1921 when Ludwig Habedandt, a physiologist at the University of Iimsbmck, showed that extracts of the corpus luteum, containing progesterone [57-83-0] C2 H2q02, could inhibit ovulation and make mice and rabbits infertile (10). Subsequent research showed that this phenomenon occurred in other species as well. 

Long-acting progestins act primarily as ovulation inhibitors. An important secondary component is their effect on the cervical mucus and endometrium, achieved at circulating blood dmg levels below those required for ovulation inhibition (40). 

In order to avoid conception, abstinence from sexual intercourse during the fertile period of the menstmal cycle must be practiced (77,104). It has been deterrnined that the fertile period in women occurs before menstmation (105,106), and formulas have been developed to determine the fertile and infertile days of the menstmal cycle. Ovulation has been linked to a cycHc shift in basal body temperature (107), which can be used retrospectively to determine the time of ovulation. 

The primary difficulty with periodic abstinence is the month-to-month variation in the time of ovulation. Whereas the ovum can only be fertilized during the first 12 to 24 hours after its release from the ovary, sperm remain viable longer in the female reproductive tract, able to fertilize an ovum for 5—7 days and perhaps longer. Thus, intercourse several days prior to ovulation can result in pregnancy. 

Studies confirm that inhibin plays a role in regulating FSH secretion. However, the importance of this role in the human has not yet been determined. If inhibin-regulated FSH secretion is pivotal in foUicular recmitment and growth, then it may be possible to block ovulation by means of inhibin antagonists. 

In addition, several progestins have been used in the absence of estrogens for purposes of contraception. It is clear that they owe their efficacy, which is not as high as that of the combination or sequential treatments, to some mechanism other than inhibition of ovulation. These are not yet represented by marketed entities for that indication. 

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